Two-dimensional few-layered Janus diamond nanofilms with boron-terminated surfaces: First-principles calculation

In this work, the structural and electronic properties of two-dimensional (111) diamond nanofilms with a layer number of n  = 3 ‒ 6 are investigated by first-principles calculation. Two kinds of Janus models (both-side boron-termination model, one-side hydrogenation and another-side boron termination model) are dynamically and thermally stable. The nanofilms have direct bandgap characteristic, and their bandgaps are tunable in a region of 2.0 ‒ 2.7 eV. The reduced bandgaps are mainly related to the surface termination of boron atoms. Interestingly, the electron mobilities (>1500 cm 2 •V   −   1 •s   −   1 ) are higher than their hole mobilities (<660 cm 2 •V   −   1 •s   −   1 ) for both models under various film thickness. The Janus structures are favorable to realize high-performance photocatalysis devices in the visible region.